Wide. Fast. Deep: Recent Advances in Multiphoton Microscopy of In Vivo Neuronal Activity

Abstract Background Amyloid precursor protein (APP) processing is central to Alzheimer’s disease (AD) etiology. As early cognitive alterations in AD are strongly correlated to abnormal information processing due to increasing synaptic impairment, it is crucial to characterize how peptides generated through APP cleavage modulate synapse function. We previously described a novel APP processing pathway producing η-secretase-derived peptides (Aη) and revealed that Aη–α, the longest form of Aη produced by η-secretase and α-secretase cleavage, impaired hippocampal long-term potentiation (LTP) ex vivo and neuronal activity in vivo. Methods With the intention of going beyond this initial observation, we performed a comprehensive analysis to further characterize the effects of both Aη-α and the shorter Aη-β peptide on hippocampus function using ex vivo field electrophysiology, in vivo multiphoton calcium imaging, and in vivo electrophysiology. Results We demonstrate that both synthetic peptides acutely impair LTP at low nanomolar concentrations ex vivo and reveal the N-terminus to be a primary site of activity. We further show that Aη-β, like Aη–α, inhibits neuronal activity in vivo and provide confirmation of LTP impairment by Aη–α in vivo. Conclusions These results provide novel insights into the functional role of the recently discovered η-secretase-derived products and suggest that Aη peptides represent important, pathophysiologically relevant, modulators of hippocampal network activity, with profound implications for APP-targeting therapeutic strategies in AD.

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Automated Extraction of Skin Wound Healing Biomarkers From In Vivo Label‐Free Multiphoton Microscopy Using Convolutional Neural Networks

Lasers in Surgery and Medicine ◽

10.1002/lsm.23375 ◽

2021 ◽

Author(s):

Jake D. Jones ◽

Marcos R. Rodriguez ◽

Kyle P. Quinn

Keyword(s):

Neural Networks ◽

Wound Healing ◽

Convolutional Neural Networks ◽

Multiphoton Microscopy ◽

Skin Wound ◽

Label Free ◽

Automated Extraction ◽

Skin Wound Healing

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Selective Targeting of Epigenetic Readers and Histone Deacetylases in Autoimmune and Inflammatory Diseases: Recent Advances and Future Perspectives

Journal of Personalized Medicine ◽

10.3390/jpm11050336 ◽

2021 ◽

Vol 11 (5) ◽

pp. 336

Author(s):

Mohammed Ghiboub ◽

Ahmed M. I. Elfiky ◽

Menno P. J. de Winther ◽

Nicola R. Harker ◽

David F. Tough ◽

...

Keyword(s):

Histone Deacetylases ◽

Inflammatory Diseases ◽

Selective Inhibition ◽

In Vivo Studies ◽

Beneficial Effects ◽

Domain Specific ◽

Recent Advances ◽

Autoimmune And Inflammatory Diseases

Histone deacetylases (HDACs) and bromodomain-containing proteins (BCPs) play a key role in chromatin remodeling. Based on their ability to regulate inducible gene expression in the context of inflammation and cancer, HDACs and BCPs have been the focus of drug discovery efforts, and numerous small-molecule inhibitors have been developed. However, dose-limiting toxicities of the first generation of inhibitors, which typically target multiple HDACs or BCPs, have limited translation to the clinic. Over the last decade, an increasing effort has been dedicated to designing class-, isoform-, or domain-specific HDAC or BCP inhibitors, as well as developing strategies for cell-specific targeted drug delivery. Selective inhibition of the epigenetic modulators is helping to elucidate the functions of individual epigenetic proteins and has the potential to yield better and safer therapeutic strategies. In accordance with this idea, several in vitro and in vivo studies have reported the ability of more selective HDAC/BCP inhibitors to recapitulate the beneficial effects of pan-inhibitors with less unwanted adverse events. In this review, we summarize the most recent advances with these strategies, discussing advantages and limitations of these approaches as well as some therapeutic perspectives, focusing on autoimmune and inflammatory diseases.

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Extracellular Release of ILEI/FAM3C and Amyloid-β Is Associated with the Activation of Distinct Synapse Subpopulations

Journal of Alzheimer s Disease ◽

10.3233/jad-201174 ◽

2021 ◽

pp. 1-16

Author(s):

Masaki Nakano ◽

Yachiyo Mitsuishi ◽

Lei Liu ◽

Naoki Watanabe ◽

Emi Hibino ◽

...

Keyword(s):

Neuronal Activity ◽

Epithelial Mesenchymal Transition ◽

Surrogate Marker ◽

Amyloid Β ◽

Dependent Manner ◽

Mesenchymal Transition ◽

Extracellular Release ◽

Activity Dependent ◽

Aβ Production

Background: Brain amyloid-β (Aβ) peptide is released into the interstitial fluid (ISF) in a neuronal activity-dependent manner, and Aβ deposition in Alzheimer’s disease (AD) is linked to baseline neuronal activity. Although the intrinsic mechanism for Aβ generation remains to be elucidated, interleukin-like epithelial-mesenchymal transition inducer (ILEI) is a candidate for an endogenous Aβ suppressor. Objective: This study aimed to access the mechanism underlying ILEI secretion and its effect on Aβ production in the brain. Methods: ILEI and Aβ levels in the cerebral cortex were monitored using a newly developed ILEI-specific ELISA and in vivo microdialysis in mutant human Aβ precursor protein-knockin mice. ILEI levels in autopsied brains and cerebrospinal fluid (CSF) were measured using ELISA. Results: Extracellular release of ILEI and Aβ was dependent on neuronal activation and specifically on tetanus toxin-sensitive exocytosis of synaptic vesicles. However, simultaneous monitoring of extracellular ILEI and Aβ revealed that a spontaneous fluctuation of ILEI levels appeared to inversely mirror that of Aβ levels. Selective activation and inhibition of synaptic receptors differentially altered these levels. The evoked activation of AMPA-type receptors resulted in opposing changes to ILEI and Aβ levels. Brain ILEI levels were selectively decreased in AD. CSF ILEI concentration correlated with that of Aβ and were reduced in AD and mild cognitive impairment. Conclusion: ILEI and Aβ are released from distinct subpopulations of synaptic terminals in an activity-dependent manner, and ILEI negatively regulates Aβ production in specific synapse types. CSF ILEI might represent a surrogate marker for the accumulation of brain Aβ.

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In Vivo Multiphoton Microscopy for Investigating Biomechanical Properties of Human Skin

Cellular and Molecular Bioengineering ◽

10.1007/s12195-010-0147-6 ◽

2010 ◽

Vol 4 (2) ◽

pp. 231-238 ◽

Cited By ~ 20

Author(s):

Xing Liang ◽

Benedikt W. Graf ◽

Stephen A. Boppart

Keyword(s):

Human Skin ◽

Multiphoton Microscopy ◽

Biomechanical Properties

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The Prototoxin lynx1 Acts on Nicotinic Acetylcholine Receptors to Balance Neuronal Activity and Survival In Vivo

Neuron ◽

10.1016/j.neuron.2006.07.025 ◽

2006 ◽

Vol 51 (5) ◽

pp. 587-600 ◽

Cited By ~ 89

Author(s):

Julie M. Miwa ◽

Tanya R. Stevens ◽

Sarah L. King ◽

Barbara J. Caldarone ◽

Ines Ibanez-Tallon ◽

...

Keyword(s):

Neuronal Activity ◽

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Nicotinic Acetylcholine

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Activation of the oxygen-sensing signal cascade prevents mitochondrial injury after mouse liver ischemia-reperfusion

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.90287.2008 ◽

2008 ◽

Vol 295 (4) ◽

pp. G823-G832 ◽

Cited By ~ 55

Author(s):

Zhi Zhong ◽

Venkat K. Ramshesh ◽

Hasibur Rehman ◽

Robert T. Currin ◽

Vijayalakshmi Sridharan ◽

...

Keyword(s):

Mitochondrial Permeability Transition ◽

Oxygen Sensing ◽

Ischemia Reperfusion ◽

Multiphoton Microscopy ◽

Specific Inhibitor ◽

Permeability Transition ◽

Heme Oxygenase 1 ◽

Mitochondrial Depolarization ◽

Signal Cascade

The mitochondrial permeability transition (MPT) plays an important role in hepatocyte death caused by ischemia-reperfusion (IR). This study investigated whether activation of the cellular oxygen-sensing signal cascade by prolyl hydroxylase inhibitors (PHI) protects against the MPT after hepatic IR. Ethyl 3,4-dihyroxybenzoate (EDHB, 100 mg/kg ip), a PHI, increased mouse hepatic hypoxia-inducible factor-1α and heme oxygenase-1 (HO-1). EDHB-treated and untreated mice were subjected to 1 h of warm ischemia to ∼70% of the liver followed by reperfusion. Mitochondrial polarization, cell death, and the MPT were assessed by intravital confocal/multiphoton microscopy of rhodamine 123, propidium iodide, and calcein. EDHB largely blunted alanine aminotransferase (ALT) release and necrosis after reperfusion. In vehicle-treated mice at 2 h after reperfusion, viable cells with depolarized mitochondria were 72%, and dead cells were 2%, indicating that depolarization preceded necrosis. Mitochondrial voids excluding calcein disappeared, indicating MPT onset in vivo. NIM811, a specific inhibitor of the MPT, blocked mitochondrial depolarization after IR, further confirming that mitochondrial depolarization was due to MPT onset. EDHB decreased mitochondrial depolarization to 16% and prevented the MPT. Tin protoporphyrin (10 μmol/kg sc), an HO-1 inhibitor, partially abrogated protection by EDHB against ALT release, necrosis, and mitochondrial depolarization. In conclusion, IR causes the MPT and mitochondrial dysfunction, leading to hepatocellular death. PHI prevents MPT onset and liver damage through an effect mediated partially by HO-1.

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